Research ArticleENGINEERING

A fully biodegradable and self-electrified device for neuroregenerative medicine

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Science Advances  11 Dec 2020:
Vol. 6, no. 50, eabc6686
DOI: 10.1126/sciadv.abc6686
  • Fig. 1 A biodegradable, self-electrified, and miniaturized conduit device for neuroregenerative medicine.

    (A) Schematic illustration of the device for sciatic nerve regeneration. The device is composed of porous PCL (~350 μm, 4.7 × 10 mm), PLLA-PTMC (~300 μm, 4.7 × 10 mm), a Mg-FeMn galvanic cell (Mg ~3.5 μm, 4.7 × 3 mm; FeMn ~1.5 μm, 4.7 × 3 mm), and electrospun PCL fibers (~30 μm, 4.7 × 10 mm). (B) Schematic exploded illustration of the device. (C) Fabrication process of the device. (D) SEM image of porous PCL. (E) SEM image of electrospun directional PCL fibers. (F) Confocal image of the guided neurite outgrowth of DRG neurons cultured on directional PCL fibers (day 7). Immunohistochemical staining: axons (β-tubulin, red), Schwann cells (S100, green), and nuclei (DAPI, blue). (G) Image of the electroactive device: front view (left) and side view (right). (H) In vivo measured OCV of an implanted device. (I) Finite element analysis of voltage (left) and electric field (right) distribution around the device on day 1 postoperatively. (J) Images collected at various stages of the accelerated dissolution of the device (planar state) in PBS (pH 7.4, 60°C). Photo credit: Liu Wang, Tsinghua University.

  • Fig. 2 In vitro DRG neuron growth behavior with Mg-FeMn galvanic cells.

    (A) Confocal microscope images of DRG neurons cultured with galvanic cells (the E-active group) and no metallic films (the control group) on day 7. The white arrow indicates the direction of the electric field. Immunohistochemical staining: axons (NF200, green), Schwann cells (S100, red), and nuclei (DAPI, blue). (B) Calcium dynamics within the DRG neurons in the E-active group (calcium, green). Left: Photo of DRG neurons after calcium dye loading. Right: Example showing the time-series imaging of calcium dynamics of the neuron in the red dashed box from the left. The cell soma was chosen as the region of interest for drawing the trace. Three images at designated time show the fluorescent intensity change. (C) Quantification of the number (left) and amplitude (right) of calcium waves within 250 s of individual neuron of the E-active and control groups (cell number: 57 in the control group; 80 in the E-active group). GraphPad Prism (version 6.0) was used for the statistical analysis, followed by unpaired t test (**P < 0.01).

  • Fig. 3 In vitro Schwann cell growth behavior with Mg-FeMn galvanic cells.

    (A) Confocal microscope images of Schwann cells of the E-active and control groups on day 3. (B) ELISA of BDNF, CNTF, NGF, and VEGF production in Schwann cells of the E-active and control groups. Data are mean ± SD. Immunohistochemical staining: Schwann cells [glial fibrillary acidic protein (GFAP), green], Schwann cells (S100, red), and nuclei (DAPI, blue). n = 3 independent experiments per group. The SPSS software package (version 23.0) was used for the statistical analysis, followed by one-way ANOVA (**P < 0.01).

  • Fig. 4 Sciatic nerve regeneration with biodegradable and electroactive conduit devices.

    (A) Surgical images of the implantation of electroactive conduit devices at the sciatic nerves of SD rats. Left: Sciatic nerves. Middle: Implantation with an autograft. Right: Implantation with an electroactive conduit device. (B) MRI images of sciatic nerves (left, no implantation) and an electroactive conduit device (right, day 7 after implantation). The white contrast at the implantation site results from swelling after surgery. (C) Micro-CT image of an electroactive conduit device (day 1 postoperatively). The black tube-like region indicates the location of the electroactive device (marked with blue lines). The white contrast on the electroactive device indicates FeMn thin films (marked with yellow dotted lines). (D) Immunofluorescent images of the transverse sections of regenerated tissues at the middle of the nerve segment at 3 weeks after implantation of the autograft, hollow, and E-active groups. The immunofluorescent images at lower magnification in the insets give the full view of regenerated tissues. Immunohistochemical staining: axons (NF200, green), Schwann cells (S100, red), and nuclei (DAPI, blue). Photo credit: Liu Wang, Tsinghua University.

  • Fig. 5 Evaluations of regenerated nerve fibers at 12 weeks after implantation of the autograft, hollow, and E-active groups.

    (A) Immunofluorescent images of the transverse section at the middle of the nerve segment (one-half section). Immunohistochemical staining: axons (NF200, green), Schwann cells (S100, red), and nuclei (DAPI, blue). (B) TEM images of the transverse sections (one-half section) of regenerated sciatic nerves. (C) Average area-based g-ratio. (D) Average diameters of myelinated axons. n = 5 independent animals per group. The SPSS software package (version 23.0) was used for the statistical analysis, followed by one-way ANOVA (**P < 0.01).

  • Fig. 6 Evaluation of gastrocnemius muscles at 12 weeks after implantation of the autograft, hollow, and E-active groups.

    (A) Representative CMAP at the injured side. Electrical stimulation (3.0 mA, 1 Hz, 0.1 ms) is applied at the proximal and distal nerve stumps. (B) Gross images of the isolated gastrocnemius muscles of the contralateral (unoperated, left) and injured side (right). (C) Masson’s trichrome staining images of the transverse sections of muscles from the injured limb. (D) Statistical analysis of CMAP amplitude at the injured side. (E) Statistical analysis of CMAP latency at the injured side. (F) Statistical analysis of the ultrasound elasticity of gastrocnemius muscles from the injured limb. (G) Statistical analysis of the wet weight ratio of the gastrocnemius muscles from the injured limb. (H) Statistical analysis of the area of muscle fibers from the injured limb quantified from Masson’s trichrome staining images. n = 5 independent animals per group. The SPSS software package (version 23.0) was used for the statistical analysis, followed by ANOVA (*P < 0.05 and **P < 0.01). Photo credit: Changfeng Lu, Chinese PLA General Hospital.

  • Fig. 7 Evaluation of the motor functional recovery of the autograft, hollow, and E-active groups.

    (A) 3D plantar pressure distribution of walking tack of SD rats at 12 weeks after implantation. A.U., arbitrary units. (B) SFI values close to 0 suggest normal motor function, while SFI values close to −100 indicate severe dysfunction. Data are mean ± SD. For each group, n = 11 for week 2; n = 8 for weeks 4, 6, and 8; and n = 5 for weeks 10 and 12. The SPSS software package (version 23.0) was used for the statistical analysis, followed by ANOVA (**P < 0.01 versus E-active group).

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